where \(R_S = 2GM/c^2\)  is the object's Schwarzschild radius.
The straightforward interpretation of Eq. (REF ) is that the amount of bending is proportional to the mass of the deflector, and inversely proportional to the distance of closest approach of the light ray to the deflector. The appearance of \(c\)  and \(G\)  is not surprising since light and gravity are involved.
Apart from a factor of two, this result can be derived from Newton's law of universal gravitation, provided that we treat a light ray as a stream of discrete particles. However, the Newtonian derivation relies on canceling out the mass of the photon, which we know to be zero. Even so, one of the great advantages of the Newtonian picture of gravity is that light bending can be understood as just one more example of classical orbital mechanics. This formulation has led to a rich literature in both astrophysics and mathematical physics (see the books [1]}, [2]}, [3]}, [4]}, [5]} and references therein).
